From a74c313aca266fab0d1d1a72becbb8b7b5286b6e Mon Sep 17 00:00:00 2001
From: Chris Packham <chris.packham@alliedtelesis.co.nz>
Date: Tue, 7 Dec 2021 17:21:44 +1300
Subject: [PATCH] i2c: mpc: Use atomic read and fix break condition
Git-commit: a74c313aca266fab0d1d1a72becbb8b7b5286b6e
Patch-mainline: v5.16-rc5
References: git-fixes

Maxime points out that the polling code in mpc_i2c_isr should use the
_atomic API because it is called in an irq context and that the
behaviour of the MCF bit is that it is 1 when the byte transfer is
complete. All of this means the original code was effectively a
udelay(100).

Fix this by using readb_poll_timeout_atomic() and removing the negation
of the break condition.

Fixes: 4a8ac5e45cda ("i2c: mpc: Poll for MCF")
Reported-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Tested-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/i2c/busses/i2c-mpc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index a6ea1eb1394e..53b8da6dbb23 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -636,7 +636,7 @@ static irqreturn_t mpc_i2c_isr(int irq, void *dev_id)
 	status = readb(i2c->base + MPC_I2C_SR);
 	if (status & CSR_MIF) {
 		/* Wait up to 100us for transfer to properly complete */
-		readb_poll_timeout(i2c->base + MPC_I2C_SR, status, !(status & CSR_MCF), 0, 100);
+		readb_poll_timeout_atomic(i2c->base + MPC_I2C_SR, status, status & CSR_MCF, 0, 100);
 		writeb(0, i2c->base + MPC_I2C_SR);
 		mpc_i2c_do_intr(i2c, status);
 		return IRQ_HANDLED;
-- 
2.31.1